VTCalendar

I'd say you missed step 4 of the installation instructions...

  Installation Instructions:
  If you have not done so already:

   1. Install the Web server software (e.g. Apache, Microsoft IIS).
   2. Install PHP 4.2 or higher. Use the latest release if possible.
   3. Install PEAR.
   4. Install the PEAR DB package.
   5. Install MySQL 4.1 or higher, or PostgreSQL. Use the latest release if possible.